This right must be set on the APPX Server. If your APPX Server is not the same machine as your PDC, please see item 1.7 for how to do this -- this right must be set at the machine level, not the domain level, for security reasons. Otherwise, just login as Administrator, and run User Manager for Domains (or just User Manager if you're using NT in a Workgroups setup).

The best way to do this, since you'll probably have lots of APPX users, is to assign this right to a group, rather than individual users. Although the quickest way to do this is to assign this right to the existing group "Everyone" or "Domain Users", it's better from a security standpoint if you create a group like "APPX Users" and assign the right only to that group. This way, you know that only users you've explicitly added to that group, have that added right. The downside is that you will have to remember to add users who will be accessing APPX to that "APPX Users" group.